Multi-speed transmission

ABSTRACT

A transmission is provided having an input member, an output member, four planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices include clutches and a brake. The torque transmitting mechanisms are selectively engageable in combinations of at least two to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is continuation of U.S. application Ser. No. 12/108,894filed on Apr. 24, 2008 and as such, under 35 U.S.C. §120, claimspriority benefit of the filing date of the above referenced application.The disclosure of the above application is incorporated herein byreference.

FIELD

The invention relates generally to a multiple speed transmission havinga plurality of planetary gear sets and a plurality of torquetransmitting devices and more particularly to a transmission havingeight or more speeds, four planetary gear sets and a plurality of torquetransmitting devices.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may or may not constitute priorart.

A typical multiple speed transmission uses a combination of frictionclutches, planetary gear arrangements and fixed interconnections toachieve a plurality of gear ratios. The number and physical arrangementof the planetary gear sets, generally, are dictated by packaging, costand desired speed ratios.

While current transmissions achieve their intended purpose, the need fornew and improved transmission configurations which exhibit improvedperformance, especially from the standpoints of efficiency,responsiveness and smoothness and improved packaging, primarily reducedsize and weight, is essentially constant. Accordingly, there is a needfor an improved, cost-effective, compact multiple speed transmission.

SUMMARY

A transmission is provided having an input member, an output member,four planetary gear sets, a plurality of coupling members and aplurality of torque transmitting devices. Each of the planetary gearsets includes first, second and third members. The torque transmittingdevices are for example clutches and brakes.

An embodiment of the transmission includes an input member, an outputmember, first, second, third and fourth planetary gear sets each havingfirst, second and third members, a first interconnecting membercontinuously interconnecting the first member of the first planetarygear set with a stationary element, a second interconnecting membercontinuously interconnecting the second member of the first planetarygear set with the third member of the second planetary gear set, a thirdinterconnecting member continuously interconnecting the third member ofthe first planetary gear set with the second member of the thirdplanetary gear set and the third member of the fourth planetary gearset, and a fourth interconnecting member continuously interconnectingthe second member of the second planetary gear set with the third memberof the third planetary gear set. Five torque transmitting mechanisms areselectively engageable to interconnect one of the first, second, andthird members with at least one of the first, second, third members, andthe stationary element. The torque transmitting mechanisms areselectively engageable in combinations of at least two to establish atleast eight forward speed ratios and at least one reverse speed ratiobetween the input member and the output member.

In one aspect of the present invention, a first of the five torquetransmitting mechanisms is selectively engageable to interconnect thefirst member of the second planetary gear set with at least one of thefirst member of the fourth planetary gear set and the input member.

In another aspect of the present invention, a second of the five torquetransmitting mechanisms is selectively engageable to interconnect thefirst member of the second planetary gear set with at least one of thesecond member of the fourth planetary gear set and the output member.

In yet another aspect of the present invention, a third of the fivetorque transmitting mechanisms is selectively engageable to interconnectthe first member of the third planetary gear set with at least one ofthe second member of the fourth planetary gear set and the outputmember.

In yet another aspect of the present invention, a fourth of the fivetorque transmitting mechanisms is selectively engageable to interconnectat least one of the second member of the first planetary gear set andthe third member of the second planetary gear set with at least one ofthe second member of the second planetary gear set and the third memberof the third planetary gear set.

In yet another aspect of the present invention, a fifth of the fivetorque transmitting mechanisms is selectively engageable to interconnectat least one of the second member of the second planetary gear set andthe third member of the third planetary gear set with the stationaryelement.

In yet another aspect of the present invention, the first members aresun gears, the second members are carrier members, and the third membersare ring gears.

In yet another aspect of the present invention, the input member iscontinuously interconnected with the first member of the fourthplanetary gear set and wherein the output member is continuouslyinterconnected with the second member of the fourth planetary gear set.

In yet another aspect of the present invention, one of the torquetransmitting mechanisms is a brake and four of the torque transmittingmechanisms are clutches.

In yet another aspect of the present invention, the stationary elementis a transmission housing.

Another embodiment of the transmission of the present invention includesan input member, an output member, first, second, third and fourthplanetary gear sets each having first, second and third members, whereinthe input member is continuously interconnected with the first member ofthe fourth planetary gear set and wherein the output member iscontinuously interconnected with the second member of the fourthplanetary gear set, a first interconnecting member continuouslyinterconnecting the first member of the first planetary gear set with astationary element, a second interconnecting member continuouslyinterconnecting the second member of the first planetary gear set withthe third member of the second planetary gear set, a thirdinterconnecting member continuously interconnecting the third member ofthe first planetary gear set with the second member of the thirdplanetary gear set and the third member of the fourth planetary gearset, and a fourth interconnecting member continuously interconnectingthe second member of the second planetary gear set with the third memberof the third planetary gear set. A first torque transmitting mechanismis selectively engageable to interconnect the first member of the secondplanetary gear set with at least one of the first member of the fourthplanetary gear set and the input member. A second torque transmittingmechanism is selectively engageable to interconnect the first member ofthe second planetary gear set with at least one of the second member ofthe fourth planetary gear set and the output member. A third torquetransmitting mechanism is selectively engageable to interconnect thefirst member of the third planetary gear set with at least one of thesecond member of the fourth planetary gear set and the output member. Afourth torque transmitting mechanism is selectively engageable tointerconnect at least one of the second member of the first planetarygear set and the third member of the second planetary gear set with atleast one of the second member of the second planetary gear set and thethird member of the third planetary gear set. A fifth torquetransmitting mechanism is selectively engageable to interconnect atleast one of the second member of the second planetary gear set and thethird member of the third planetary gear set with the stationaryelement. The torque transmitting mechanisms are selectively engageablein combinations of at least two to establish at least eight forwardspeed ratios and at least one reverse speed ratio between the inputmember and the output member.

In one aspect of the present invention, the first members are sun gears,the second members are carrier members, and the third members are ringgears.

In another aspect of the present invention, the stationary element is atransmission housing.

Another embodiment of the transmission of the present invention includesan input member, an output member, first, second, third and fourthplanetary gear sets each having a sun gear, a carrier member and a ringgear, wherein the input member is continuously interconnected with thesun gear of the fourth planetary gear set and wherein the output memberis continuously interconnected with the carrier member of the fourthplanetary gear set, a first interconnecting member continuouslyinterconnecting the sun gear of the first planetary gear set with astationary element, a second interconnecting member continuouslyinterconnecting the carrier member of the first planetary gear set withthe third member of the second planetary gear set, a thirdinterconnecting member continuously interconnecting the ring gear of thefirst planetary gear set with the carrier member of the third planetarygear set and the ring gear of the fourth planetary gear set, and afourth interconnecting member continuously interconnecting the carriermember of the second planetary gear set with the ring gear of the thirdplanetary gear set. A first torque transmitting mechanism is selectivelyengageable to interconnect the sun gear of the second planetary gear setwith at least one of the sun gear of the fourth planetary gear set andthe input member. A second torque transmitting mechanism is selectivelyengageable to interconnect the sun gear of the second planetary gear setwith at least one of the carrier member of the fourth planetary gear setand the output member. A third torque transmitting mechanism isselectively engageable to interconnect the sun gear of the thirdplanetary gear set with at least one of the carrier member of the fourthplanetary gear set and the output member. A fourth torque transmittingmechanism is selectively engageable to interconnect at least one of thecarrier member of the first planetary gear set and the ring gear of thesecond planetary gear set with at least one of the carrier member of thesecond planetary gear set and the ring gear of the third planetary gearset. A fifth torque transmitting mechanism is selectively engageable tointerconnect at least one of the carrier member of the second planetarygear set and the ring gear of the third planetary gear set with thestationary element. The torque transmitting mechanisms are selectivelyengageable in combinations of at least two to establish at least eightforward speed ratios and at least one reverse speed ratio between theinput member and the output member.

In one aspect of the present invention, the stationary element is atransmission housing.

Further objects, aspects and advantages of the present invention willbecome apparent by reference to the following description and appendeddrawings wherein like reference numbers refer to the same component,element or feature.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way;

FIG. 1 is a lever diagram of an embodiment of an eight speedtransmission according to the present invention;

FIG. 2 is a diagrammatic view of an embodiment of an eight speedtransmission according to the present invention; and

FIG. 3 is a truth table presenting the state of engagement of thevarious torque transmitting elements in each of the available forwardand reverse speeds or gear ratios of the transmission illustrated inFIGS. 1 and 2.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

At the outset, it should be appreciated that in the particular exampleprovided, the eight speed automatic transmission of the presentinvention has an arrangement of permanent mechanical connections betweenthe elements of the four planetary gear sets. These mechanicalconnections generically link or relate the transmission embodiments.More specifically, a first component or element of a first planetarygear set is permanently coupled to a ground. A second component orelement of the first planetary gear set is permanently coupled to afirst component or element of a second planetary gear set. A thirdcomponent or element of the first planetary gear set is permanentlycoupled to a second component or element of a third planetary gear setand also to a first component or element of a fourth planetary gear set.Finally, a second component or element of the second planetary gear setis permanently coupled to a first component or element of the thirdplanetary gear set.

Referring now to FIG. 1, an embodiment of an eight speed transmission 10is illustrated in a lever diagram format. A lever diagram is a schematicrepresentation of the components of a mechanical device such as anautomatic transmission. Each individual lever represents a planetarygear set wherein the three basic mechanical components of the planetarygear are each represented by a node. Therefore, a single lever containsthree nodes: one for the sun gear, one for the planet gear carrier, andone for the ring gear. The relative length between the nodes of eachlever can be used to represent the ring-to-sun ratio of each respectivegear set. These lever ratios, in turn, are used to vary the gear ratiosof the transmission in order to achieve an appropriate ratios and ratioprogression. Mechanical couplings or interconnections between the nodesof the various planetary gear sets are illustrated by thin, horizontallines and torque transmitting devices such as clutches and brakes arepresented as interleaved fingers. Further explanation of the format,purpose and use of lever diagrams can be found in SAE Paper 810102, “TheLever Analogy: A New Tool in Transmission Analysis” by Benford andLeising which is hereby fully incorporated by reference.

The transmission 10 includes an input shaft or member 12, a firstplanetary gear set 14 having three nodes: a first node 14A, a secondnode 14B and a third node 14C, a second planetary gear set 16 havingthree nodes: a first node 16A, a second node 16B and a third node 16C, athird planetary gear set 18 having three nodes: a first node 18A, asecond node 18B and a third node 18C, a fourth planetary gear set 20having three nodes: a first node 20A, a second node 20B and a third node20C and an output shaft or member 22.

The input member 12 is coupled to the third node 20C of the fourthplanetary gear set 20. The output member 22 is coupled to the secondnode 20B of the fourth planetary gear set 20. The first node 14A of thefirst planetary gear set 14 is coupled to a ground, stationary elementor a transmission housing 50. The second node 14B of the first planetarygear set 14 is coupled to the first node 16A of the second planetarygear set 16. The third node 14C of the first planetary gear set 14 iscoupled to the first node 20A of the fourth planetary gear set 20. Thefirst node 20A of the fourth planetary gear set 20 is coupled to thesecond node 18B of the third planetary gear set. The second node 16B ofthe second planetary gear set 16 is coupled to the first node 18A of thethird planetary gear set 18.

A first clutch 26 selectively connects the third node 16C of the secondplanetary gear set 16 with the third node 20C of the fourth planetarygear set 20 and with the input member 12. A second clutch 28 selectivelyconnects the third node 16C of the second planetary gear set 16 with thesecond node 20B of the fourth planetary gear set 20. A third clutch 30selectively connects the third node 18C of the third planetary gear set18 with the second node 20B of the fourth planetary gear set 20 and theoutput member 22. A fourth clutch 32 selectively connects the secondnode 14B of the first planetary gear set 14 and the first node 16A ofthe second planetary gear set 16 with the first node 18A of the thirdplanetary gear set 18 and the second node 16B of the second planetarygear set 16. A brake 34 selectively connects the first node 18A of thethird planetary gear set 18 and the second node 16B of the secondplanetary gear set 16 with the stationary element or the transmissionhousing 50.

Referring now to FIG. 2, a stick diagram presents a schematic layout ofthe embodiment of the eight speed transmission 10 according to thepresent invention. In FIG. 2, the numbering from the lever diagram ofFIG. 1 is carried over. The clutches, brake and couplings arecorrespondingly presented whereas the nodes of the planetary gear setsnow appear as components of planetary gear sets such as sun gears, ringgears, planet gears and planet gear carriers.

For example, the planetary gear set 14 includes a sun gear member 14A, aring gear member 14C and a planet gear carrier member 14B that rotatablysupports a set of planet gears 14D (only one of which is shown). Planetgears 14D are each configured to intermesh with both the sun gear member14A and the ring gear member 14C. The sun gear member 14A is connectedto a stationary element or the transmission housing 50 by a first shaftor interconnecting member 42 in order to restrict the sun gear member14A from rotating relative to the transmission housing 50. The ring gearmember 14C is connected for common rotation with a second shaft orinterconnecting member 44. The planet carrier member 14B is connectedfor common rotation with a third shaft or interconnecting member 46.

The planetary gear set 16 includes a sun gear member 16C, a ring gearmember 16A and a planet gear carrier member 16B that rotatably supportsa set of planet gears 16D (only one of which is shown). Planet gears 16Dare each configured to intermesh with both the sun gear member 16C andthe ring gear member 16A. The sun gear member 16C is connected forcommon rotation with a fourth shaft or interconnecting member 48. Thering gear member 16A is connected for common rotation with third shaftor interconnecting member 46. The planet carrier member 16B is connectedfor common rotation with a fifth shaft or interconnecting member 52 anda sixth shaft or interconnecting member 54.

The planetary gear set 18 includes a sun gear member 18C, a ring gearmember 18A and a planet gear carrier member 18B that rotatably supportsa set of planet gears 18D (only one of which is shown). Planet gears 18Dare each configured to intermesh with both the sun gear member 18C andthe ring gear member 18A. The sun gear member 18C is connected forcommon rotation with a seventh interconnecting member 56. The ring gearmember 18A is connected for common rotation with sixth shaft orinterconnecting member 54. The planet carrier member 18B is connectedfor common rotation with an eighth shaft or interconnecting member 58.

The planetary gear set 20 includes a sun gear member 20C, a ring gearmember 20A and a planet gear carrier member 20B that rotatably supportsa set of planet gears 20D (only one of which is shown). Planet gears 20Dare each configured to intermesh with both the sun gear member 20C andthe ring gear member 20A. The sun gear member 20C is connected forcommon rotation with the input shaft or member 12. The ring gear member20A is connected for common rotation with second shaft orinterconnecting member 44 and with eighth shaft or interconnectingmember 58. The planet carrier member 20B is connected for commonrotation with a ninth interconnecting shaft or member 60 and outputshaft or member 22.

The input shaft or member 12 is preferably continuously connected to anengine (not shown) or to a turbine of a torque converter (not shown).The output shaft or member 22 is preferably continuously connected witha final drive unit or transfer case (not shown).

The torque transmitting mechanisms or clutches 26, 28, 30, 32 and brake34 allow for selective interconnection of the shafts or interconnectingmembers, members of the planetary gear sets and the housing. Forexample, the first clutch 26 is selectively engageable to connect theinput shaft or member 12 with the fourth shaft or interconnecting member48. The second clutch 28 is selectively engageable to connect the fourthshaft or interconnecting member 48 with the ninth shaft orinterconnecting member 60. The third clutch 30 is selectively engageableto connect the seventh shaft or interconnecting member 56 with the ninthshaft or interconnecting member 60. The fourth clutch 32 is selectivelyengageable to connect the third shaft or interconnecting member 46 withthe sixth shaft or interconnecting member 54. The brake 34 isselectively engageable to connect the fifth interconnecting shaft ormember 52 with the stationary element, ground, or the transmissionhousing 50.

Referring now to FIGS. 2 and 3, the operation of the embodiment of theeight speed transmission 10 will be described. It will be appreciatedthat transmission 10 is capable of transmitting torque from the inputshaft or member 12 to the output shaft or member 22 in at least eightforward speed or torque ratios and at least one reverse speed or torqueratio with a single overdrive. Each forward and reverse speed or torqueratio is attained by engagement of one or more of the torquetransmitting mechanisms (i.e. first clutch 26, second clutch 28, thirdclutch 30, fourth clutch 32 and brake 34), as will be explained below.FIG. 3 is a truth table presenting the various combinations of torquetransmitting mechanisms that are activated or engaged to achieve thevarious gear states. Actual numerical gear ratios of the various gearstates are also presented although it should be appreciated that thesenumerical values are exemplary only and that they may be adjusted oversignificant ranges to accommodate various applications and operationalcriteria of the transmission 10. An example of the gear ratios that maybe obtained using the embodiments of the present invention are alsoshown in FIG. 3. Of course, other gear ratios are achievable dependingon the gear diameter, gear teeth count and gear configuration selected.

To establish reverse gear, the first clutch 26 and brake 34 are engagedor activated. The first clutch 26 connects the input shaft or member 12with the fourth shaft or interconnecting member 48. The brake 34connects the fifth interconnecting member 52 with the stationary elementor the transmission housing 50. Likewise, the eight forward ratios areachieved through different combinations of clutch and brake engagement,as shown in FIG. 3.

It will be appreciated that the foregoing explanation of operation andgear states of the eight speed transmission 10 assumes, first of all,that all the clutches and brake not specifically referenced in a givengear state are inactive or disengaged and, second of all, that duringgear shifts, i.e., changes of gear state, between at least adjacent gearstates, a clutch or brake engaged or activated in both gear states willremain engaged or activated.

The description of the invention is merely exemplary in nature andvariations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A transmission comprising: an input member; an output member; first,second, third and fourth planetary gear sets each having first, secondand third members; a plurality of interconnecting members continuouslyinterconnecting one of the first members, second members, and thirdmembers of the planetary gear sets with another one of the firstmembers, second members, and third members of the planetary gear sets,and a stationary element; a first torque transmitting mechanismselectively engageable to interconnect the first member of the secondplanetary gear set with the first member of the fourth planetary gearset; a second torque transmitting mechanism selectively engageable tointerconnect the first member of the second planetary gear set with thesecond member of the fourth planetary gear set; a third torquetransmitting mechanism selectively engageable to interconnect the firstmember of the third planetary gear set with the second member of thefourth planetary gear set; a fourth torque transmitting mechanismselectively engageable to interconnect the second member of the firstplanetary gear set with the second member of the second planetary gearset; and a fifth torque transmitting mechanism selectively engageable tointerconnect the second member of the second planetary gear set with thestationary element, and wherein the torque transmitting mechanisms areeach selectively engageable in combinations of at least two to establishat least eight forward speed ratios and at least one reverse speed ratiobetween the input member and the output member.
 2. The transmission ofclaim 1 wherein a first of the plurality of interconnecting memberscontinuously interconnects the first member of the first planetary gearset with the stationary element.
 3. The transmission of claim 2 whereina second of the plurality of interconnecting members continuouslyinterconnects the second member of the first planetary gear set with thethird member of the second planetary gear set.
 4. The transmission ofclaim 3 wherein a third of the plurality of interconnecting memberscontinuously interconnects the third member of the first planetary gearset with the second member of the third planetary gear set and the thirdmember of the fourth planetary gear set.
 5. The transmission of claim 4wherein a fourth of the plurality of interconnecting memberscontinuously interconnects the second member of the second planetarygear set with the third member of the third planetary gear set.
 6. Thetransmission of claim 1 wherein the first members are sun gears, thesecond members are carrier members, and the third members are ringgears.
 7. The transmission of claim 1 wherein the input member iscontinuously interconnected with the first member of the fourthplanetary gear set and wherein the output member is continuouslyinterconnected with the second member of the fourth planetary gear set.8. The transmission of claim 1 wherein the stationary element is atransmission housing.
 9. A transmission comprising: an input member; anoutput member; first, second, third and fourth planetary gear sets eachhaving first, second and third members, wherein the input member iscontinuously interconnected with the first member of the fourthplanetary gear set and the output member is continuously interconnectedwith the second member of the fourth planetary gear set; fourinterconnecting members continuously interconnecting one of the first,second, and third members of the planetary gear sets with another one ofthe first members, second members, and third members of the planetarygear sets, and a stationary element; a first torque transmittingmechanism selectively engageable to interconnect the first member of thesecond planetary gear set with the first member of the fourth planetarygear set; a second torque transmitting mechanism selectively engageableto interconnect the first member of the second planetary gear set withthe second member of the fourth planetary gear set; a third torquetransmitting mechanism selectively engageable to interconnect the firstmember of the third planetary gear set with the second member of thefourth planetary gear set; a fourth torque transmitting mechanismselectively engageable to interconnect the second member of the firstplanetary gear set with the second member of the second planetary gearset; and a fifth torque transmitting mechanism selectively engageable tointerconnect the second member of the second planetary gear set with thestationary element, and wherein the torque transmitting mechanisms areeach selectively engageable in combinations of at least two to establishat least eight forward speed ratios and at least one reverse speed ratiobetween the input member and the output member.
 10. The transmission ofclaim 9 wherein a first of the four interconnecting members continuouslyinterconnects the first member of the first planetary gear set with thestationary element.
 11. The transmission of claim 10 wherein a second ofthe four interconnecting members continuously interconnects the secondmember of the first planetary gear set with the third member of thesecond planetary gear set.
 12. The transmission of claim 11 wherein athird of the four interconnecting members continuously interconnects thethird member of the first planetary gear set with the second member ofthe third planetary gear set and the third member of the fourthplanetary gear set.
 13. The transmission of claim 12 wherein a fourth ofthe four interconnecting members continuously interconnects the secondmember of the second planetary gear set with the third member of thethird planetary gear set.
 14. The transmission of claim 13 wherein thefirst members are sun gears, the second members are carrier members, andthe third members are ring gears.
 15. The transmission of claim 14wherein the stationary element is a transmission housing.
 16. Atransmission comprising: an input member; an output member; first,second, third and fourth planetary gear sets each having a sun gear, acarrier member and a ring gear; a first interconnecting membercontinuously interconnecting the sun gear of the first planetary gearset with a stationary element; a second interconnecting membercontinuously interconnecting the carrier member of the first planetarygear set with the ring gear of the second planetary gear set; a thirdinterconnecting member continuously interconnecting the ring gear of thefirst planetary gear set with the carrier member of the third planetarygear set and the ring gear of the fourth planetary gear set; a fourthinterconnecting member continuously interconnecting the carrier memberof the second planetary gear set with the ring gear of the thirdplanetary gear set; a first torque transmitting mechanism selectivelyengageable to interconnect the sun gear of the second planetary gear setwith at least one of the sun gear of the fourth planetary gear set andthe input member; a second torque transmitting mechanism selectivelyengageable to interconnect the sun gear of the second planetary gear setwith the carrier member of the fourth planetary gear set and the outputmember; a third torque transmitting mechanism selectively engageable tointerconnect the sun gear of the third planetary gear set with thecarrier member of the fourth planetary gear set and the output member; afourth torque transmitting mechanism selectively engageable tointerconnect at least one of the carrier member of the first planetarygear set and the ring gear of the second planetary gear set with atleast one of the carrier member of the second planetary gear set and thering gear of the third planetary gear set; and a fifth torquetransmitting mechanism selectively engageable to interconnect at leastone of the carrier member of the second planetary gear set and the ringgear of the third planetary gear set with the stationary element, andwherein the torque transmitting mechanisms are each selectivelyengageable in combinations of at least two to establish at least eightforward speed ratios and at least one reverse speed ratio between theinput member and the output member.
 17. The transmission of claim 16wherein the stationary element is a transmission housing.
 18. Thetransmission of claim 16 wherein the input member is continuouslyinterconnected with the sun gear of the fourth planetary gear set andthe output member is continuously interconnected with the carrier memberof the fourth planetary gear set.